Oxidation of alcohols



Aug. 19, 1947. c, HULL 2,425,879

OXIDATION OF ALCOHOLS Filed July 8, 1944 METER conosnscn 27 STE-AM 9 L23SEPARATOR oxmmon UNIT 2* PACKED 2T? 22 SCRUBBER RECEIVER JJW Y f r JJJ2e 44 RECEIVER OXIDIZING MEDIUM D V") C, HULL V DVVENTUR v A Ys PatentedAug. .19, 1947 UNITED STATES PATENT OFFICE OXIDATION OF ALCOHOLS David0. Hull, Kingsport, Tenn assignor to Eastman Kodak Company, Rochester,N. Y., a

corporation of New Jersey Application July .8, 1944, Serial No. 544,0004 Claims. (01. 260-531) verting ethanol to acetic acid, before myinvention it was considered necessary to first dehydrogenate 2polyhydroxy alcohols and similar organic compounds, invention is toprovide a direct oxidation process which may be operated at relativelylow tem-v peratures and under ordinary pressure conditions, yet givevery satisfactory yields of the desired oxidation products. Stillanother object is to provide a direct oxidation process for theconversion'of alcohols to acids wherein the alcohol may be converted,not only to an acid having a number of carbon atoms corresponding to anumber of carbon atoms in the alcohol molecule, but also to a differentacid. A still further object is to provide a process which may beoperated under all of the ethanol and thereafter the aldehydic otherthan normal atmospheric conditions, dehydrogenation product wasconverted to the namely, under either superatmospheric or reacid which,as can be seen, involves a number of duced pressures. steps. A furtherobject is to provide a direct oxida- Carrying out oxidation processes inaccordance tion proc s tha m y be pl d to i h with the prior artpossesses a number of disadalcohols alone or mixtures of alcohols andaldevantages exemplified, for example, by the required hydes, or othertypes of mixtures. A still further use of relatively high temperatures.Also there object is to provid a direct, low-temperature may in someinstances be the disadvantag of oxidation process which may be appliedto various polymerization of the products and of the startmixtures ofalcohols and aldehydes' wherein both ing materials accompanied by lowyields and the alcohol and the aldehyde are converted into other losses.

In my U. S. Patent 2,287,803 I have described a process for a moredirect oxidation of organic compounds. While the process of myapplication functions very satisfactorily and gives good yields inrelatively few steps, it involves the utilization of metals having anatomic number from 25 to 29.. t

It is, therefore, apparent that it is desirable, particularly underpresent conditions to develop a process in order that other metals maybe employed and the process improved in other respects, as will beapparent from the description which follows.

After further investigation I have found that there are certan othercatalytic materials which may be employed in direct oxidation processesin a manner akin to the procedure set forthin my U. S. Patent 2,287,803,which not only permits obtaining direct oxidation, but permits theproduction. of a relativelylarger variety of products than hasheretofore been obtainable.

This invention has for one object to provide a process for the directoxidation of organic compounds. Another object is to provide a .directoxidation process which is particularly valuable for the directconversion of lower aliphatic alcohols to lower aliphatic acids insubstantially a single step. Still another object, however, is toprovide a process which may be applied, not only to the monohydroxyalcohols, but also td the useful oxidation products. to provide a directoxidation process, particularly adapted to the treatment of alcoholssuch as butyl' alcohol'and the like wherein, not only may butyric acidbe obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquidsparticularly adapted for employment in the aforesaid types of processesfor the direct conversion of alcohols alone, or alcohols in variousadmixtures, into useful oxidation products. A still further object is toprovide methods for producing the catalysts as well as for activatingand utilizing the catalysts.

As already indicated, prior to my invention if an alcohol were to beoxidized it was generally first dehydrogenated and then thedehydrogenation products further treated. In any event, prior artprocesses as applied to alcohols usually involve the utilization oftemperatures'in excess of 300 C., which, not only requires substantialheat input, but, due to the higher temperatures and other conditionsrequired in handling chemicals, involves dangers of loss frompolymerization or other undesired reactions. Also apparatus destructionmay be more severe.

I have found that contrary to such procedure an organic compound,exemplified in particular by a hydroxy compound as a lower aliphaticalcohol, may be directly oxidized at relatively low Another andparticular object of this Another object is denser l9 into separator 2|.

temperatures, even temperatures substantially below 100 0., with any ofthe usual oxidizing mediums of which the commonest one, namely air, maybe readily utilized in my process. Also my process, after it is placedin operation, does not usually require any heat input but generatessufficient heat itself to maintain the reaction. Not only may singleorganic compounds be treated, but various mixtures of the organiccompounds may be treated. For example, I have found that a mixturecomprising a lower aliphatic alcohol, together with a corresponding oradifferent aldehyde, may be efllciently treated by my novel process andcatalyst to give very high yields of aliphatic acid. By my process andchoice of catalyst it is possible to obtain one or more acids in theoxidation procedure. The foregoing features, as well as features oftreating various mixtures under different conditions, will be set forthin de tail hereinafter.

While the oxidation procedure may be carried out in the apparatusdescribed in my U. S. Patent No. 2,287,803, for convenience ofconsideration and for a better understanding of the present inventionreference will be made to the attached drawing. The single figurethereof may be considered a semi-diagrammatic side elevation viewshowing a general apparatus arrangement which could be employedforcarrying out my process.

Referring to the drawing, 2 represents an exidation unit which maycomprise any of several different constructions. For example, thepreferred external construction would, in a large di-' ameter unit, bein accordance with Hasche Patent 2,159,988. However, the constructionmay be a sieve plate column, bubble plate column, or other comparablearrangement for permitting the contact of an oxidizing medium containingtree oxygen with the material to be oxidized. In the unit shown in theattached figure the column merely comprises an elongated, open column ofrelatively narrow dimensions. Attached to the-lower part of the unit at3 and 4 are, cooling jackets provided with inlets for cooling medium asat 6 and I.

The upper part of the unit was provided similar Jacket 8; however, inthis jacket, rather than cooling medium some heating medium may becirculated in the event that high boiling components are being directlyoxidized or the reaction temperature is to be held lower than that whichwould maintain a constant volume of catalyst. Inasmuch as theconstruction is substantially the same, however, the mechanicalconstruction would be approximately the same and an inlet provided at 9,1 and 6; outlets are provided at l|.l2,and|3.

As indicated, if desired in place of the external jackets, coils may beincluded within the unit and in large-size units such arrangementwherein internal coils, or both coils and jackets are em ployed, may bedesirable.

The lower part of the unit is provided with a plurality of inletconduits, namely, inlet conduit H which is connected with atemperature-controlled feed supply It. Also leading into the lower partof the unit is an inlet conduit 11 for oxidizing medium.

,The upper part of the unit is provided with a drawoff conduit l8 whichleads through con- This separator has attached thereto a receiver 22 forcondensate and a branch conduit 23 through which'non-condensables "maybe conducted to the scrubber 24.

The aforementioned scrubber is provided with a receiver 26 at the lowerpart thereof a d V t with a conduit 21 from the upper part thereof,which may lead through a meter or other device for measuring and testingthe eflluents.

There may also be associated with the apparatus thermometers or othertemperature controlling devices or various exchangers for recoveringheat or otherwise facilitating or rendering the operation of the processmore economical, or permitting it to be operated with automatic control.Hence, my invention is not to be restricted in these respects.

1 have found that silver may be incorporated in acidic solutions andthat thes solutions will function as a catalyst medium for the directoxidation of organic compounds. That is, an alcohol alone or an alcoholand other organic compounds to be oxidized, may be passed into acatalyst solution, as aforementioned, in the presence of an oxidizingmedium containing free oxygen and the alcohol may be directly oxidizedto acid, as will be observable from the specific data which follow.

In preparing catalyst solutions for use in the present process, anyconvenient source of the metal may be employed, such as salts, oxides,or other derivatives thereof. Preferably a derivative will be chosenwhich is easily soluble under the conditions of the process. Forexample, assuming that it is desired to convert an aliphatic a1- coho1such as ethanol or butanol directly to the corresponding aliphatic acid,the derivative of the catalyst metal may be silver acetate.

While the aforementioned metal derivative may be employed in variousorganic liquids,

which are solvents therefor, for simplicity of operation and minimizingthe necessity of complivfor several hours.

- cated separations I prefer to dissolve the catalyst compound in aliquid principally composed of one of the materials which is to beproduced in the process. For example, in the event my process were to beapplied in converting butyl alcoholdirectly into butyric acid I wouldpreferably dissolve the catalyst compound in an aliphatic acid such asbutyric acid, although, propionic or acetic acid could also be used.However, for initially preparing the catalyst solution other liquidscould be employed, as for example, organic esters and the like such asbutyl or ethyl acetate.

In an event, irrespective of the exact metal compound and the liquidthat the compound is dissolved in, the catalyst solution would be givena vigorous oxidation treatment such as blowing with a substantial amountof air, usually for a period of at least 5 or 10 minutes, and ifdesired,

This treatment would be accompanied by the introduction of an aldehydealong with the oxidizing medium which functions to convert the metalions of the catalyst metal into a higher state of valence valence. Thetreatment may be accompanied by heating obtained in any convenientmanner, such as by flowing a-heating medium in the jackets or coils inassociation with the oxidation unit or by introducing heated air. Thetemperature 'of treatment, however, may varyfrom around 0C up to theboiling point of the particular liquid present. In other wordsthe-solution is maintained under liquid phase conditions.

It is also preferred to incorporate the oxidizing medium into thecatalyst liquid under at least atmospheric pressure as this permits theinclusion of a larger amount of oxidizing medium and fully saturates thecatalyst liquid.

After the catalyst liquid containing silver as already described hasbeen treated and brought than their lowest That is, referring to theattached drawing, the

oxidation column 2 is filled with the catalyst liquid comprising silveracetate dissolved in the solvent and maintained at the desiredtemperature. The hydroxy compound to be oxidized is introduced into theoxidation process through conduit I 4 and the oxidizing mediunnusuallyair (although pure oxygen or ozone'may be employed and appear to renderthe catalyst solution more active, but are not necessary), and thecompound oxidized to one or more desired oxidation products, as will bedescribed hereinafter. Assuming that the oxidation product is a liquid,a portion thereof may be volatilized or pumped off through conduit l8through the condenser i9 where condensables are condensed out to becol-,- lected in receiver 22. The unconsumed gases (as nitrogen when airis used as oxidizing medium), unoxidized organic compounds and the likecomponents, u ncondensed,pa ss through conduit 23 into scrubber 24 wherethey are recovered. While only a single scrubbingunit has beenindicated, a plurality of such units may be employed or other recoverydevices utilized.

The operation of my process to convert-an organic compound such as ethylalcohol, propyl alcohol, butyl alcohol or other: aliphatic hydroxycompounds to the desiredacidsandthe function of the metal compound asaldehyde activated catalyst is quite clearlyillustrated by the data theoxidation, while the major portion of the remaining alcohol was leftunchanged. As indicated, while at normal atmospheric pressure, atemperature under 100 C. appears to be'quite satisfactory, theparticular temperature selected will be determined largely by referenceto the particular alcohol tobe oxidized and. whether the process is tobe operated under pressure or merely at atmospheric pressure. Forexample, in the case of ethyl, propyl, or butyl alcohol, I prefer atemperature range of C. to 50 C.

Under preferred operating conditions as, for

example, when air is used as the oxidant, this may be supplied undersome pressure and, if desired, a rather substantial excess may beemployed, although for normal operations merely an excess is required;that is, such an amount that a few per cent of oxygen will be present inthe eiliuents. In the event of the use of other oxidants such asrelatively pureoxygen and ozone smaller amounts are required and may besupplied under substantial pressure to cause them fully to permeate theentire catalyst solution;

The oxidation of any given alcohol in accordance with my process may beaccomplished by activating the catalyst metal in the solution by meansof a single aldehyde or by a plurality of aldehydes. Forlgexample, inoxidizing ethyl alcohol, I may employ acetaldehyde, propionaldehyde, orbutyraldehyde alone or two or more of them. Moreover, I may oxidizeethyl alcohol, propyl alcohol, butyl alcohol or amyl alcohol, byemploying any one or more of aldehydes such as acetaldehyde,propionaldehyde, butyraldehyde,

appearing in the following table:' and so on. However, inasmuch asacetaldehyde Q Percent Grams Percent Percent Grams Grams Percent GramsGrams Example 533 g g A HAO HGBu' Conversion HOP! 23, 25: HOAc fig gso}. Fed Produced to HOBu it Produced Produced ROM:

1 Ag s 234.4 124 12.3 4.32 14.5 6 {c at Percent Metal I Metal Salt Gramsof Examples Acetate in cat.v lrams Alcohol Fed HA0 Fed Yie'lgclldto Acidor Acids n x 3.5 560 EthylAlc 375 91.8 100% Acetic. ,III Ag 2.7876NormallropylAlc.... 880 85.3 90% HOPr, 10% HOAc.

The foregoing examples were carried out in apparatus as indicated inthe-attached drawing and at a temperature between 30 C. and C., .althouh a'*wider range'of temperatures, such -5 C. to 150C. could be employedsatisfactorily.

It will be observed from theabove table that I'.

have employed a relatively small amount of the metal acetate inthecatalyst solution in the examples given, but'this' may be variedrather widely. For example, I mayuse anywhere from i 1 or 2% ofthe'metal acetate upto 12% or more. While the foregoing examples areillustrative of preferred embodiments of -xmy invention, it will beevident that many modifications therein may be made within the scope ofthe inventive concept involved. As previously, indicated, the silvercatalyst may be used under the conditions outlined above for theconversion of various aliphatic alcohols to acids. It may be employed inthe form of a single salt or mixtures of salts of any desired organicacid or acids.

In the above examples, there was some small percentage of alcoholconverted to lower acids and to .esters in addition to the mainproductof is in many instances most readily available and has a low boilingpoint, it would preferably be employed along with other alcohols such asbutyl alcohol, amyl alcohol, and the like, as representing the mosteconomical procedure, as well as tending to lower the boiling-points andpermit the functioning of the'process at the lowest practicaltemperatures.

As already indicated, the pressure, may be varied over wide limitswithout basically changing the process. However, since the processfunctions satisfactorily under normal atmospheric pressures, I prefer tooperate under such conditions. In some instances, such as for saturatingthe catalyst solution with oxygen, I may apply a few pounds pressure upto 2 or 3 atmospheres for this purpose. Also, as indicated, the processsuillcient supply of aldehyde in the catalyst solution to obtain thedesired catalyst activity. By

to the acid having the same number of carbon atoms as the alcohol beingoxidized may be varied by choice of the particular catalyst.

It is apparent from the foregoing that my invention is applicable to thedirect oxidation of the various organic compounds, particularly hydroxycompounds such as various alcohols. The foregoing data are merelyillustrativeflof some of the materials to which my low temperatureliquid phase process may be applied, but variousjother compounds, suchas hydroxy alcohols exemplified by glycols, may be treated in acomparable man ner. Hence, I do not wish to be restricted in myinvention except insofar as is necessitated by the prior art and thespirit of the appended claims What I claim and desire to secure byLetters Patent of the United States is:

1. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of silver in an aliphatic acid with an aldehyde and a gaseousoxidizing medium to form an active catalyst solution, introducingmaterial amounts of a lower aliphatic alcohol and a lower aliphaticaldehyde into the activated catalyst solution, oxidizing the alcohol ofthe resulting solution of catalyst, alcohol and aldehyde to thecorresponding acid by treating said solution with a gaseous oxidizingmedium, maintaining the temperature of the solution of catalyst, alcoholand recovering the aliphatic acid produced.

aldehyde during its treatment with the gaseous oxidizing medium suchthat the solution is'main-- tained in the liquid phase, and subsequentlyrecovering the aliphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of silver in an aliphatic acid with an aldehyde and a gaseousoxidizing medium to form an active catalyst solution, introducingmaterial 3. The process of claim 2'1n.which the catalyst, alcohol andaldehyde is maintained during its treatment with the gaseous oxidizingmedium at a temperature of 30 C. to C.

4. A process for the direct oxidation of a lower aliphatic alcohol toobtain an acid mixture containing a major proportion of an acidcorresponding to the alcohol being oxidized and a minor proportion of anacid having a less number of carbon atoms than the alcohol, whichcomprises treating a solution of silver in an aliphatic' acid with analdehyde and a gaseous oxidizing medium to form an active catalystsolution, introducing material amounts of a lower aliphatic alcohol anda lower aliphatic aldehyde into the activated c'atalyst solution,oxidizing the alcohol of the resulting solution of catalyst, alcohol andaldehyde by treating said solution with a gaseous oxidizing medium,maintaining the temperature of the solution of catalyst, alcohol andaldehyde during its treatment with the gaseous oxidizing medium suchthat the solution is maintained in the liquid phase, and subsequentlyrecovering the aliphatic acid produced.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,285,914 Drossbach June 9, 19422,263,607 Bludworth Nov. 25, 1941 2,287,803 Hull June 30, 1942 2,265,948Loder Dec. 9, 1941 FOREIGN PATENTS Number Country Date 111,050 AustraliaJuly 25, 194(

